EFFECT OF ORGANIC AND INORGANIC AMENDMENTS ON THE HEAVY METAL CONTENT OF SOIL AND WHEAT CROP IRRIGATED WITH WASTEWATER

Field experiment was conducted to study the effect of wastewater irrigation and different organic and inorganic amendments on the phytoavailability of metals to wheat crop. Wheat was grown in (2x1 m plot) irrigated with wastewater generated from HIE (Hayatabad Industrial Estate, Peshawar, Pakistan) and municipal wastes during 2008. Five different amendments viz farm yard manure (FYM), poultry manure (PM), diammonium phosphate (DAP), triple super phosphate (TSP) and humic acid (HA) were applied and mixed with soil prior to crop growing. In addition, a control (Tubewell irrigation TW) and only wastewater (WW) irrigation plot (without amendments) was also set up for comparison. The FYM and PM were applied at the rate of 10 tons ha^-1. The DAP and TSP were added @ of 150 kg ha^-1 as P where as HA was added @ of 1.5 kg ha^-1. A Basal dose of N and K @ of 120 and 60 kg respectively were also added to all experimental plots except control. The results showed that wheat yield and yield components were significantly increased with the addition of all the amendments compared to control and the higher increase was noted in HA treated plots. The effect of different amendments applied on AB-DTPA extractable metals was significant for Cu, Fe, Mn, Ni and Pb (P 0.05) and non significant for Cd, Cr and Zn. Higher concentration were noted in the wastewater applied plots with exception of Zn that was lowest in wastewater irrigated plots. The effect of all the amendments on AB-DTPA extractable metals was comparable with exception of Pb that was significantly reduced by DAP. It was concluded that all the metals under study were below the toxicity level in soil and none of the essential nutrient was deficient. The leaves metal concentrations showed that higher values of all the metal under study were noted in leaves when irrigated with WW and TW irrigated plants resulted minimum accumulation of metals in leaves. The effect of different amendments on the plant uptake of metal was variable. Addition of HA reduced the uptake of Cd, Cr, Mn whereas DAP was effective in reducing the phytoavailability of Pb and Zn.